Polyester printing roller



May 21, 1963 A. E. RAYMOND 3,090,106

POLYESTER PRINTING ROLLER Filed June 26, 1959 50 WMMEW ,4770 /YEYS tates This invention relates to printing or inking'rollers used to accept ink from a supply fountain or the like and convey and transfer this ink to a printing plate.

More particularly this invention relates to a roller having an inking surface layer of a cast rubbery organic polymer which prints With the quality of. composition, eg., glue and glycerine type, rollers While possessing durability, environmental insensitivity, dimensional stability and ability to handle inks more closely akin to synthetic rubber rollers, e.g., Neoprene, yarid B una rubbers and the like. While the invention has particular reference to ink form rollers, namely those inking rollers which contact the printing surface of a printing plate, the invention is not limited to inking rollers in theform position but applies to any roller in lghe train of inking rollers, (including speck or hickey scavenging rollers), used on a printing press to control the transfer of ink from a supply fountain to a printing plate on a press. h

Rollers are conventionally formed of an axial shaft having an intermediate cylindrical enlargement on which a rubbery inking surface layer is provided by casting, or Wrapping and then vulcanizing. I'he ends of the shaft serve as journals for rotation in printing press bearings.

There are numerous variations to this construction. Thus, it has been known to rst cover the cylindrical enlargement With a sponge or soft rubbery layer and thereafter apply to it or some subsequent layer a surfacing layer of ink transferring rubber or the like. Another procedure, which has recently been introduced, isthat of providing a vacuum contractible rubber body, of either natural or synthetic rubber, on the roller enlargement and over this body slipping a removable sleeve which sleeve is provided with a surfacing layer of the particular composition to be used as the ink transfer composition..

Regardless of how the surfacing layer is to be applied, whether as the integral body of the roller or as a surfacing layer on a removable sleeve fitting over the roller body, or otherwise, this invention pertains to printing or inking rollers having at least as the surfacing layer thereof a rubbery organic polymer of a carboxyl terminated organic polyester cured with an N,Nbis1,2alkylene amide of a dicarboxylic acid. Such polyesters are disclosed in application Serial No. 668,038, led June 26, 1958, by Watkins et al., now abandoned, and the polymers and method of their formation described therein is incorporated hereinto by reference.

Rollers surfaced with these new inking surfacings more nearly combine the desirable properties of composition and synthetic rubber rollers than has heretofore been possible. While composition rollers are inexpensive, capable of formation by casting in molds, possess excellent surface tackiness and are known to provide printing of the highest quality, their short press lives, low dimensional stability, and inability to withstand moisture and heat restrict their use to low speed letterpress printing presses. On the other hand while synthetic and natural rubber rollers are durable, heat and moisture resistant, and 'are capable of handling a larger variety of inks than are composition rollers, their printing quality does not compare with that of the composition rollers. For these gains, however, the rubbers and synthetic rubbers sacrifice good surface tack or thumb appeal and printing quality. Further, with the exception of the polyurethane rubbers, they cannot be cast in molds and necessitate slow, laborious hand labor in their formation. The various types of rollers are compared and contrasted in the American Pressman, January and February 1959 issues, parts 1 and 2 of the article entitled, Printing Rollers by James K. Brown.

The rollers of this invention can, like composition and polyurethane synthetic rubber rollers, be cast in molds and provide printing quality which appears to match that of composition rollers coupled with durability and other characteristics closely akin to those of synthetic rubber rollers, including the polyurethane syntlietics.

These new printing rollers have a tackiness or surface feel of the type usually associated with composition rollers, and at least the surface layer thereof comprising a rubbery organic polymer of a carboxyl terminated polyester of a polyol and a polycarboxylic acid, which polyester is modified with and cured by the addition thereto of a N,Nbisl,2alkylene amide of a dicarboxylic acid. The N,Nbisamide and the polyester are combined so that there is at least one amide group for each reactive carboxylic group of the polyester, and to this end about 30% more than the stoichiometric equivalent amount of amide required to react with the free carboxyl groups is normally utilized in the reaction mixture.

The polyester may be formed from any convenient combination of branched chain or ether oxygen containing alkylene diols and dicarboxylic acids compatible with N,Nbisl,2alkylene amide to provide a pourable or castable system capable of curing to solid rubbery organic polymers useful as printing roller surfacings.

Useful polyesters have been found to be those formed from branched or ether oxygen containing alkylene diols containing between 3 and about 8 carbon atoms, such as 1,2-propylene glycol, 1,3-butylene glycol, neopentyl Vglycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and the like, and alkylene dicarboxylic acids wherein the alkylene group is from 2 to about 110 carbon atoms in total, as for example, succinic, adipic, diglycolic, azelaic, sebacic, and isosebacic acids. These compounds are combined to provide polyesters having acid numbers (calculated by end group determination) from about 30 to 60.

In addition, a minor amount of a polyfunctional material having more than two reactive hydrogens, usually in the form of reactive OH or COOH groups, is included in the alkylene diol and dibasic acid mixture to provide crosslinking sites on the polyester chain, such polyfunctional iriolecules being exempliiied by glycerol, trimethylol propane, trimesic acid, citric acid, tricarboxylic acid, and the like. Of course the functionality may be greater than trifunctionality as provided by compounds such as pentaerythritol or benzene tetracarboxylic acid. The amount of such material to be added is calculated to provide an average of from about 1li to about l branch of such material per polyester molecule.

The N,N'bis-l,2alkylene amides to be used are those corresponding to the general formula:

RiHC CHR;

wherein R represents a member of the group consisting of alkylene radicals having from 4 to 18 carbon atoms and single ring arylene radicals such as the 1,3-phenylene and 1,4-phenylene radicals and R1 and R2 represent a member of the group consisting of hydrogen and lower alkyl radicals, from l to about 3 carbon atoms in length.

Fillers, extenders, pigments, catalysts and modiers may be added to the castable composition as desired yto stiften, reinforce, increase abrasion resistance and tensile strength or otherwise tailor the properties of the solid rubber polymers as required. Also, antioxidants to stabilize against aging can be added to enhance the utility of the polymers as printing roller surfacing layers.

Printing rollers exhibiting excellent printing characteristics have been made from trimethylol propane modified lglycol-acid polyesters cross-linked with N,N'bis ethylene isosebacamide. These rollers possess a characteristic tacky feel approximating that of glue-glycerine type rollers and believed responsible for their superior printing quality. These new rollers combine this feel with adequate toughness, heat and abrasion resistance, dimensional stability, elastic recovery and solvent .resistance for high speed, long time printing use on high speed lithoand letterpress printing presses, the latter use being more demanding than similar utility as inking rollers on the lithopress, e.g., planographic printing, usually from rotary offset presses printing from lithographic plates. These rollers have also been found to be useful in the held of prin-ting with glycol-based inks (such as used in the food- !Wrapper printing), which inks decompose glue-glycerine and polyurethane rollers. Fur-ther, these new surfacings are heat resistant to temperatures `in the order of 320 F., indicating their utility in very high speed printing operations.

In the accompanying drawing there is illustrated in FIGURE l -a diagrammatic view of a rotary oifset lithographic printing press; in FIGURE 2 there is illustrated a roller made in accordance with the teachings of this invention; and, in FIGURE 3, there is illustrated a vacuum contractible roller having a removable sleeve mounted thereon, which sleeve has an inking surface layer thereon formed in accordance with lthe teachings of this invention.

Referring first specifically -to FIGURE l there is disclosed therein schematically a typical rotary offset press construction designated in its entirety by the numeral 10. It is -to be understood that this is illustrative only of one general type of printing press in which `the rollers of this invention have particular utility. Basically, insofar as roller use is involved, this -type of press distinguishes from Ia letterpress in that in a letterpress the ink form rollers contact a relief image printing plate having raised inking surfaces Whereas in an olfset press, the form rollers contact smoother surfaced planographic plates. The roller trains 14 and 12 are exemplary of ink supplying `and ink repellant supplying sys-tems. The ink form roller positions are those contacting the plate cylinder and the ink form rollers are designated by the numeral l16.

In FIGURE 2 of the drawing Ithe conventional roller construction is shown wherein -an elongated shaft 1S having a cylindrical enlargement `2G intermediate the ends thereof is provided with a rubbery body of a bisamide cured polyester as hereinbefore described designated by the numeral 22.

In FIGURE 3, there is disclosed a vacuum contractible roller body 24 formed in accordance with the procedure outlined in copending application Serial No. 694,549, now

abandoned, supra, the roller body containing circumferentially spaced longitudinal passages 26 into which the rubbery body 24 of the roller contracts upon the application of 4a vacuum to the passages thereby reducing the diameter of the roller body. Over lthis roller body is mounted a removable sleeve 28 of a nonstretchable tubular core 30 having an inside diameter in-termediate the reduced and normal 4diameters of the rubbery body 24 and surfaced with a rubbery polymer 32 of a bisamide cured polyester.

The formative steps of making the rollers and evaluating their performance are given in the specific examples which follow, which examples it is to be understood are for purposes of illustration only and not determinative of the scope of the invention.

EXAMPLE l Printing rollers were produced from the following liquid The glycol, acid and trimethylol propane were mixed together and air driven out by bubbling ni-trogen therethrough. Thereafter a vacuum was applied to a kettle containing the mixture at -a temperature of about 200 C. for several hours to provide :an acid terminated polyester, having a theoretical acid number of about 50.7, with an lactual acid number in the range `of 50' to 55. The polymer displayed an average degree 'of polymerization of 25.2 units/mol (each unit being calculated las one half of the total molecular weight of the repeating unit formed by the reaction of one ethylene glycol molecule with one acid molecule in the polyester chain.) The amount of trirnethylol propane added was calculated to provide approximately one half of a trimethylol propane branch on the polymer chain for each polyester molecule, these branches serving as crosslinking or branching sites in the further formation of the polymer. The -branching calculation is within the gelation equation system of P. S. Flory in his Principles of Polymer Chemistry, Cornell Press, Ithica, N.Y., 1953, pages 347 to 397.

To 6 par-ts by weight of the polyester thus formed was added one part by Weight of N,N-bis-ethylene isosebacarnide. The resulting liquid mass was poured into the open top of an upstanding cylindrical mold, the inside `of which had been coated with ra silicone release composition. Concentrically disposed within the mold was a roller shaft with the ends thereof projecting through the ends of the mold so that 4only the cylindrical enlargement of the shaft was disposed in the mold, spaced from the wall of the mold about 1/2 of an inch (radially). The liquid mixture was poured into the mold to fill the same. After filling, the mold twas placed in an oven -at 250 F. for about 2 hours to cure the bisamide containing polyester. The roller, when removed from the mold had a clear, almost water white surfacing 'layer thereon of solid rubbery bisarnide cured polyester. The roller displayed a durometer, Shore durometer A2 scale, of about 35, and by virtue of the longitudinal passages therethrough, was vacuum contractible in the manner described in copeuding application Serial No. 694,549, supra.

EXAMPLE 2 Inking roller sleeves, for mounting on contractible roller bodies made in accordance with the procedures of application Serial No. 694,549, supra, were made by mounting a paper sleeve core on a metal mandrel and placing the same in a closed mold 'of the type noted hereinabove with respect to the roller formation, the sleeve core being radially spaced concentrically inwardly about 1A inch from the inner wall surface of the cylindrical mold. The mold space was evacuated and Ithe bisamide containing liquid polyester mixture was drawn into the mold space; the iilled mold was then placed in an oven at about 250 for two hours to cure the sleeve.

Following the procedure just outlined a number of sleeves were prepared for various sized -rollers utilizing various bisamide cured products of the polyester formulations listed hereinbelow:

Polyester Formulations Trimethylol propane .0485 Acid No. between about 53-58; degree of polymerization 27.3 units/mol.

Sleeve surfacing layers were formed by mixing each of the polyesters and mixtures thereof with N,Nbis ethylene isosebacamide, the latter compound being added in a 30% excess of the stoichiometric amount necessary to react with all the free carboxyl groups yof the polyester in crosslinking the polyester, and curing the resultant mixtures to rubbery solids. The following formulations were utilized in the sleeve surfacing layer construction:

Bz'samde Cured Polyester F annulations 1 Pts. by wt. Polyester B 843 Polyester A 457 N,Nbisethylene isosebacamide (20 durometer) 175 Polyester A 1300 N,N'bisethylene isosebacamide (35 durometer) 210 3 Polyester B 1300 N,Nbisethylene isosebacamide 156 Aging stabilizer of a fatty acid amide (Versamide 140, marketed by General Mills) reaction product of a polyamine and a fatty acid durorneter) 26 Polyester B 7 84 Polyester C 466 N,Nbisethylene -isosebacamide 177 Versamide 140 (20 durometer) 25 Polyester C 1200 N,N'bisethylene isosebacamide 216 Versarnide 140 (15 durometer) 24 The sleeve cores were stiff, tubular, nonelastic members made up of 3 layers of spirally wrapped, elastomer irnpregnated paper, the center spiral layers being spirally wound in the same direction as the outer layer and in an opposite direct-ion to the inner spiral layer of the core. A moisture and hydrocarbon solvent resistant permanent adhesive laminated the spiral wraps to one another in the formation of the sleeve core.

Sleeves of this nature have been made for and used on diierent printing presses, both letterpress and rotary offset lithographie press rollers having been surfaced with these sleeves. The sleeve surface layer durometers varied from about 10 to 35 on the Shore A2 scale.

EXAMPLE 3 T o test the printing quality of the sleeves against the printing quality of commercially used glue-glycerine, or composition type, rollers, reflection densitometer readings were taken on copy printed with the sleeves surfaced with the tive compositions noted in the previous example on copy printed with a glue-glycerine roller, on a Miller Simplex 20" x 26" letterpress, the ynumerical designation referring to the maximum sheet size that can be used in the press. Test conditions for all yof the sleeves were identical and the tests were carried out by placing the surfacings to be tested in the ink form roll position on the press, there being two form rollers. Five sets of the nonstretchable sleeves surfaced with the ve compositions noted in the previous example were mounted on vacuum contractible form rollers on the press and the printing quality compared with glue-glycerine rollers.

Each set of rollers was run for 15,000 impressions.

As each set of rollers was changedl new packing and makeready were applied to the press so that the conditions of the tests would be as identical as possible.

All of the tests were carried out with a form sheet oomposed of and 133 line screens with tones of 910%, 80%, 70%, 60%, 25% and 10% as well as solid cuts, one running parallel to the printing cylinder and the other perpendicular to the printing cylinder. All printing plates were 11 point copper electrotypes mounted on a honeycomb base. The ink utilized in all of the tests was a consolidated quick set halftone black and the densitometer readings taken on 60# coated enamel paper printed with this ink. Ink fountain settings on the press were constant for all sleeves and rollers tested.

Reflection densitometer readings were taken with a densitometer, which comprises a light meter in a light box with a iilter over the light opening. The particular filter to be used is chosen by Iobtaining a zero reading on the light reilectance scale of the meter on a solid color printed on the paper and a reading of 100 on the scale on the unprinted portions of the paper. Consequently, the smaller the number the darker the printing.

A completely black surface is a 100% tone surface and will produce a reading of zero and 4the halftone, i.e., anything less than a solid cut; eg., a tone is one wherein 90% of the area is colored and 10% -is uncolored, an 80% is where 80% of the area is colored and 20% uncolored, etc., causing higher readings. In general when comparing sleeve and roller readings, a lower reading signiiies superiority on solid cuts and a higher reading superiority on halftones.

Anything less than a tone, or solid cut, is generally referred to in the artt as a halftone, be it a 10% or 90% colored area. The toning is achieved by do-ts produced by light exposure through a screen on a negative, which negative is in turn reproduced on the plate and the plate subsequently etched. The idelity of the printing color is determined by the number of dots per inch; for example 133 dots per linear linch being used for high iideli-ty, halftone printing on iine stocks and 85 dots per linear inch being used for coarser stock such as newspapers.

In the tables which follow it is to be understood that in the halftone areas, the higher numbers, which designated the lighter reading on the scale of the densitometer, are the more desirable whereas on the solid areas of the scale the lower readings indicate the better quality. The lengthwise extending solid area represents a longitudinal stripe on the printed sheet from the leading, or gripper edge of the paper to the trailing edge. Characteristically, this stripe darkens from the gripper to the trailing edge; however, uniformity of color is the effect strived for.

EXAMPLE 4 Solid area vfact, some 6 TABLE L FIRST IMPRESSION Percent herlftone` and No, line screen glue `glycerin@ in printrollers under he test 'conditions ufilized.l In of the sleeves out-performed the with cotton cloths and weighed immediately and checked for volume increase. The results are shown in the table below:

l10 the tack was lost, however, there was no tendency of the roller sleeve to glaze and printing quality remained excellent.

TABLE V Polyester #1 #2 #3 #4 #5 Solvent Weight Vol. Weight Vol. Weight Vol. Weight Vol. Weight Vol. inc. inc. inc. inc. ine. inc. inc. inc. inc. inc. percent percent percent percent percent percent percent percent percent percent NTn.-A:Raw linseed oil B=Light mineral oil C: Kerosene D: Mineral spirit; E=Varnish makers and painters naphtha; FzTap water.

Compression set tests, carried out by compressing samples of polyesters 1-5, 60% form their original height and maintaining the compression force for 48 hours at about 72 F., revealed that after release of the compressing force, the average compression set for the samples was less than 5%.

As will be noted from the solvent resistance data, these rubbery polymers are quite easily modified to fit any particular ink base. Thus, where rubbery polymer No. 5, for example, is not suitable in naphthas and mineral spirits because of the weight increase and volume swell, polymer No. 2 is excellent in this regard.

Significantly, all of these rubbery polymers are suitable for use with ethylene glycol based inks. Polyurethane rollers, the only other cast rubbery rollers utilized in the printing trade, which rollers generally appear to comprise polyesters of diethylene glycol and adipic acid cured with mixed isomers of toluene diisocyanate and plasticized with a phosphate ester cannot be used with glycol based inks as the glycol base decomposes the polymer. Also significant, from another point of view, the N,N-bisamide cured polyester rubbers forming the inking surface layers of this invention contain no plasticizers, which sometimes tend to migrate and flow under conditions of use and surface grinding.

EXAMPLE 5 N,N-bisamide cured polyester rubbery polymer surfaced sleeves have been run in the ink form roll positions on both letter-press printing presses and offset lithopress printing presses under prin-t shop conditions and have performed satisfactorily.

Sleeves surfaced with polymer No. 2 of Example l mounted on vacuum contractible rollers in the ink form roll positions on a Davidson model 241 ten inch lithopress, a small rotary offset press, produced consistently high quality printing copy over long periods of time without loss of roundness or dimensional stability, remaining unaffected by temperature and humidity changes, changing ink bases, or ordinary cleaning solvents used to wipe the surfaces clean.

Similar sleeves surfaced with polymer No. l of Example l on the ink form roll positions of a Miehle 29 letterpress, a small flatbed press, produced consistently high quality printed copy for millions of impressions with no special care in cleaning or handling and without glazing or hardening of any kind. Further, these sleeve surfacings could and were ground down on a commercial grinding machine to provide clean printing surfaces without diiculty or deterioration. The newly exposed surfaces possessed the same characteristic tacky feel as the original surfaces and printed with the same high quality. This tacky feel appeared to last approximately twice as long as the tacky feel lasts on a glue-glycerine roller. When Thus, the rubbery polymers of this invention, when used on the most difficult inking positions on both letterpress and lithopress printing presses performed well to provide excellent printing copy while maintaining their dimensional stability and durability, thereby combining composition roller printing quality with the synthetic rubber durability. j

What I claim is as follows:

l. A printing roller having ends thereon for journaling in bearings of a printing press, a resilient cylindrical roller body intermediate said roller ends, said roller body having at least as the surfacing layer thereof for transferring printing ink from a supply source to a printing plate a solid tacky surfaced rubbery polyester cured with a N,N bis-1,2-alkylene amide of a dicarboxylic acid, said polyester comprising the polymeric reaction product of an alkylene diol containing between about 3 and about 8 carbon atoms in the alkylene group, an alkylene dicarboxylic acid containing from about 2 to about l0 carbon atoms in the alkylene group, and a minor amount of a polyfunctional organic compound having more than two reactive hydrogens.

2. A printing roller having ends thereon for journaling in bearings of a printing press, a resilient cylindrical roller body having at least as the surfacing layer thereof for transferring printing ink from a supply source to a printing plate a solid tacky surfaced rubbery polyester cured with a N,Nbisl,2alkylene amide of a dicarboxylic acid, said polyester comprising the polymeric reaction product of an alkylene diol containing between about 3 and about 8 carbon atoms in the alkylene group, an alkylene dicarboxylic acid containing from about 2 to about l0 carbon atoms in the alkylene group, and a minor amount of a polyfunctional organic compound having more than two reactive hydrogens, said N,Nbisamide having from l to 5 carbon atoms in each of said 1,2-alkylene groups, and said dicarboxylic acid forming said amide being selected from the group consisting of alkylene dicarboxylic acids containing from 4 to 18 carbon a-toms inthe alkylene radicals and single ring arylene dicarboxylic acids.

3. A printing roller having ends thereon for journaling in bearings of a printing press, a resilient cylindrical body intermediate said ends comprising an ink conveying and transferring layer for conveying ink from a supply source to a printing plate, said layer having a soft, tacky feeling surface and comprising a solid rubbery, nonporous branched chain carboxyl terminated polyester cured with a N,N-bis-l,2alkylene amide, said carboxyl terminated polyester having an acid number of between about 30 and 60 and comprising the reaction product of a branched chain -glycol of from 3 to about 8 carbon atoms, an alkylene dicarboxylic acid wherein the alkylene group contains from about 2 to about 10 carbon ato-ms, and a minor 3,090,106 11 12 amount of a hydrocarbon polyol containing at least three References Cited in the file of this patent reactive hydroxyl groups, said bisamide being the amide of a dicarboxylic acid selected from the group consisting UNITED STATES PATE-NTS of alkylene dicarboxylic acids wherein the alkylene radi- 2,594,145 F1013 Apr 22, 1952 cal contains from 4 to 18 carbon atoms in the alkylene 5 2,694,695 Melamed NOV- 16, 1954 radical, and single ring arylene dicarboxylic acids.

4. The roller of claim 3 wherein said surfacing layer FOREIGN PATENTS is on a removable sleeve. 749,541 Great Britain May 30, 19576 

1. A PRINTING ROLLER HAVING ENDS THEREON FOR JOURNALING IN BEARINGS OF A PRINTING PRESS, A RESILIENT CYLINDRICAL ROLLER BODY INTERMEDIATE SAID ROLLER ENDS, SAID ROLLER BODY HAVING AT LEAST AS THE SURFACE LAYER THEREOF FOR TRANSFERRING PRINTING INK FROM A SUPPLY SOURCE TO A PRINTING PLATE A SOLID TACKY SURFACED RUBBERY POLYESTER CURED WITH A N,N''BIS-1,2-ALKYLENE AMIDE OF A DICARBOXYLIC ACID, SAID POLYESTER COMPRISING THE POLYMERIC REACTION PRODUCT OF AN ALKYLENE DIOL CONTAINING BETWEEN ABOUT 3 AND ABOUT 8 CARBON ATOMS IN THE ALKYLENE GROUP, AN ALKYLENE DICARBOXYLIC ACID CONTAINING FROM ABOUT 2 TO ABOUT 10 CARBON ATOMS IN THE ALKYLENE GROUP, AND A MINOR AMOUNT OF A POLYFUNCTIONAL ORGANIC COMPOUND HAVING MORE THAN TWO REACTIVE HYDROGENS. 